Although there have been many attempts to make collapsible shipping containers of molded resin materials, these containers have not been large enough and strong enough for holding 300 gallons or more of liquid materials. Such a size and capacity is desirable for the loading of trucks and railroad cars; and the ability to hold liquid materials is desirable for shipping food products, chemicals, and many pourable, bulk materials. Collapsibility is desirable so that empty containers are compact on return shipment.
Collapsible metal containers have been made strong enough for these purposes; but they are expensive, heavy, and easily damaged. Non-collapsible and non-reusable containers have also succeeded, but these tend to be more expensive than collapsible and reusable containers.
The invention involves a way of making resin walls of a collapsible shipping container strong enough so that the container can be used repeatedly for shipments of about 300 gallons or more of liquid and comparable density materials. The inventive solution allows a collapsible container to take advantage of the desirable characteristics of molded resin, while being large enough and strong enough to meet the shipping needs of many materials.